A conventional objective lens drive unit adjusts the position of the objective lens in the direction of focusing by sliding a lens holder (objective lens) inserted in a support shaft in the direction of the optical axis and along the support shaft by means of an electromagnetic force obtained by the interaction between current which energizes a focusing coil and a magnetic field, and also adjusts the position of the objective lens in the direction of tracking by rotating the lens holder about the support shaft by means of an electromagnetic force obtained by the interaction between current which energizes a tracking coil and a magnetic field.
Patent Document 1: Japanese Patent Application Laid-Open No. 8-203102 (page 7, FIG. 3, FIG. 5)
Patent Document 2: U.S. Pat. No. 33,548
The above-described conventional objective lens drive unit is unsuitable for size reduction since a magnetic circuit for obtaining the electromagnetic force in the direction of the optical axis and a magnetic circuit for obtaining the electromagnetic force in the direction of rotation about the support shaft are provided separately.
Further, another pair of magnetic circuits are additionally required in the case of forming a three axis lens shifting mechanism for implementing an image blur correcting function and an automatic focusing function of an image capturing apparatus applying the above-described objective lens drive unit, which is further unsuitable for size reduction.
Furthermore, in the above-described conventional objective lens drive unit, the lens holder is slid or rotated about the support shaft, which causes a nonnegligible influence by friction. Therefore, a structure is presented in which a balancing weight is provided in a position substantially symmetric to the objective lens with respect to the support shaft, to thereby make the center of gravity of the lens holder agree with the position of the support shaft, so that the influence by friction is minimized. With such structure, however, the weight of a movable part is increased by the balancing weight, thus requiring a greater amount of driving force, which is not suitable for reducing consumption power.